Properties of passive film formed on CP titanium, Ti-6Al-4V and Ti-13.4Al-29Nb alloys in simulated human body conditions

The passive film behavior of CP Titanium, Ti-6Al-4V and Ti-based intermetallic Ti-13.4Al-29Nb was investigated as a function of immersion time in simulated body condition (Hank's solution), utilizing potentiodynamic polarization and electrochemical impedance spectroscopy techniques. All the alloys were spontaneously passivated on immersion in the electrolyte. Potentiodynamic polarization experiments conducted after 1 and 168 h of immersion in Hank's solution indicated similar passive current densities. The susceptibility of Ti-13.4Al-29Nb alloy for passive film breakdown was ascribed to the greater Al content in the alloy. Electrochemical impedance spectroscopy studies indicated that the resistance of the passive film increased with duration of immersion for CP Titanium and Ti-13.4Al-29Nb. Therefore, the order of corrosion resistance under simulated human body conditions is Ti-Nb>Ti>Ti-V.